In quantum optics, a cat state is defined as the coherent superposition of two coherent states with opposite phase:

Phase control in a coherent superposition of degenerate quantum states through frequency control.

The nature of measurements and of the coherent superposition in this theory also gives rise to the quantum phenomenon of interference.

The interaction of matter with light, i.e., electromagnetic fields, is able to generate a coherent superposition of excited quantum states in the material.

Further applications concern the coherent superposition of non-optical wave fields.

As an example, superselection rules for electric charges disallow the preparation of a coherent superposition of different charge eigenstates.

If the photon has a non-zero probability to take either path, then it is in a coherent superposition of the two states:

These coherent superpositions of the two possible states are called qubits and are the basic ingredient of Quantum information science.

The molecule is now in two states at the same time: it resides in a coherent superposition of states.

The coherent superposition of wave amplitudes is called first order interference.